Size-distribution analysis of potentially formed blocks during the primary fragmentation of a fractured rock

The in‐situ primary fragmentation that occurs during mining operations (using caving methods) highly depends on pre‐existing fractures. Slip along fracture planes and breakage of rock bridges are the main controls of the fragmentation and block formation process during caving.

Itasca's Role

The method is applied at three locations (named left, center, right) of the studied rock mass, each time in a volume of side 10 m.

Figure 1 shows the three cumulative fragment volume distributions arising from the three DFN (with no rock bridge breakage) and 2D cut views of the blocks. We use an approach (available in 3FLO) based on 3D DFN-based image analysis. Erosion/dilation algorithms are used to assess block (fragment) size distributions. Blocks are defined first by the DFN geometry. The analysis then yields the block‐size distribution created by the breakage of rock bridges of any given size.

Figure 2 shows the cumulative volume distribution obtained by accounting for rock bridge breakage up to 0.6 m. Note that, unlike the initial distributions, which exhibit significant discrepancies between the different locations, these results are very similar from one location to the other. According to these results, it is estimated that 50% of blocks will have a volume larger than 0.8 to 1 m3.

Project Results

With the 3D DFN‐based image analysis we are able to:

Estimate the size distribution of blocks obtained during the primary fragmentation of a fractured rock.

Estimate how an increase in the size of broken rock bridges affects the sizes of the resulting blocks.